My context for "learning" Imperial is solely based on measurements of length. I've "learned" it b/c i listen to a lot of US-Centric carpentry podcasts. I've just memorized 1 inch ~ 2.54 cm ; 3/8 inch ~ 1 cm. Most other fraction can be derived from those in the head. At least enough for following a carpentry podcast.
When i need more precision, i use an online converter or a ruler with an imperial and a metric scale. FWIW i only think in metric.
When i need more precision, i use an online converter or a ruler with an imperial and a metric scale. FWIW i only think in metric.